This invention relates to a throttle valve position signal correcting apparatus for use with an automotive vehicle having an automatic transmission and an internal combustion engine from which a drive is transmitted to the automatic transmission.
Throttle valve position sensors have been used to sense a position of an throttle valve provided for controlling the amount of air permitted to enter to engine cylinder. The sensed throttle valve position is used to control the engine and transmission. For example, Japanese Utility Model Kokai No. 1-144451 discloses a conventional apparatus for correcting the throttle valve position signal to absorb throttle sensor characteristic variations and errors occurring when the throttle valve is assembled in the engine. The conventional apparatus is arranged to use a value of the throttle valve position signal sensed when the engine speed remains in a predetermined range for a time longer than a predetermined value to correct the throttle valve position signal. However, the conventional apparatus fails to provide an appropriate correction when an accessory such as an air conditioning unit or the like operable on power from the engine. When the air conditioning unit is operating, a fast idle unit operates to hold the throttle valve at a fast idle (somewhat open) position so as to increase the engine idling speed at engine idle conditions. For this reason, the throttle valve position signal value sensed when the engine is judged to be idling with the air conditioning unit being operating is different from the throttle valve position signal value sensed when the engine is judged to be idling with the air conditioning unit being not operating. If the throttle valve position signal is corrected with the air conditioning unit being operating, the corrected throttle valve position signal indicates a throttle valve position smaller than the actual throttle valve position. Consequently, the corrected throttle valve position is not suitable for transmission position change and line pressure controls.